There are electronic devices including a plurality of slots for installing plug-in units (PIU) such as interface cards and control cards. In this kind of electronic device, an electronic component mounted on the plug-in unit is uniformly cooled by air blown from a blower fan that is provided below the slots (see, for example, Japanese Laid-open Patent Publications Nos. 2005-109334, 2001-177281, and 2003-332776).
With the increasing capabilities of electronic components mounted on plug-in units in recent years, the amount of heat generated by these electronic components tends to increase. Therefore, under the current circumstances, it is difficult to sufficiently cool electronic components that generate large amounts of heat by the above-mentioned method of cooling electronic components mounted on plug-in units.